Classical observables from coherent-spin amplitudes

The quantum field-theoretic approach to classical observables due to Kosower, Maybee and O’Connell provides a rigorous pathway from on-shell scattering amplitudes to classical perturbation theory. In this paper, we promote this formalism to describe general classical spinning objects by using coherent spin states. Our approach is fully covariant with respect to the massive little group SU(2) and is therefore completely synergistic with the massive spinor-helicity formalism. We apply this approach to classical two-body scattering due gravitational interaction. Starting from the coherent-spin elastic-scattering amplitude, we derive the classical impulse and spin kick observables to first post-Minkowskian order but to all orders in the angular momenta of the massive spinning objects. From the same amplitude, we also extract an effective two-body Hamiltonian, which can be used beyond the scattering setting. As a cross-check, we rederive the classical observables in the center-of-mass frame by integrating the Hamiltonian equations of motion to the leading order in Newton’s constant.

Dynamics of two particles on a vertically driven plate

We experimentally investigate the dynamics of two particles driven vertically and free to collide in a nearly one-dimensional channel. Both spherical particles are Delrin with a diameter of d = 5.0 mm. We obtained data for driving frequencies, f, ranging from 26.06 to 29.52 HZ and acceleration magnitudes, Γ, from 1.79 to 2.42 g. High speed digital imaging is used to extract the positions of the two particles from experiment, with digital imaging analysis used to extract velocities and accelerations from sequential images. The total energy and the velocity of the particles before and after collisions are studied in both the lab frame and centre of mass frame. Most of the experimental results suggest a linear dependence for the relative velocity after collision on the relative velocity before collision with the coefficient of restitution approximately constant at 0.8. However, some data in the low impact velocity regime indicates the possibility of an occasional energy transfer between the rotational and translational degrees of freedom.

Addressing the two-step scenario of high-energy ion collisions with 136Xe + p and 136Xe +12 C at 1 A.GeV in inverse kinematics, at the SPALADiN setup of GSI

We have measured at GSI-Darmstadt (Germany) the reactions 136 Xe + p and 136 Xe +12 C, using the inverse-kinematics technique at 1 A.GeV and the large acceptance SPALADiN setup. The combination of both provides a very good coverage of the phase-space of the excited system decay channels, allowing the study of the relative importance of those decay channels, as well as a very efficient filter to reject from the detection the particles and nuclear fragments of high energy in the projectile centre-of-mass frame, essentially produced in the first-instant nucleon-nucleon collisions, prior to the decay of the excited nuclear system. Our analysis in the two-step scenario permits one to estimate on an event basis E*/A, the excitation energy per nucleon of the decaying nuclear system, and to study the E*/A dependence of the different decay channels. The E*/A range of overlap of the 136 Xe + p and 136Xe+12 C reactions is large and allows for an extensive comparison between both reactions, and therefore provides a strong test bench of the entrance-channel-independence hypothesis of the excited-system decay. We address the two-step-scenario assumption in the light of our data and their comparison with different up-to-date models.

Elastic scattering phase shift generalizations to two spin-3 2 particles: On the determination of Ω–Ω scattering phase amplitudes in elongated boxes

The relationship between the elastic scattering phase shifts of the [Formula: see text] system and the two-particle energy spectrum in elongated boxes is established in center-of-mass frame under periodic boundary conditions. The formulas are also extended to cubic boxes to confirm the results in elongated boxes. Our analytical results will be helpful to the study of [Formula: see text] interaction on lattice by using Lüscher’s finite volume method.

Super-Penrose process

If two particles collide near a rotating black hole, their energy in the centre of mass frame can become unbounded under certain conditions. In doing so, the Killing energy [Formula: see text] of debris at infinity is, in general, remain restricted. If [Formula: see text] is also unbounded, this is called the super-Penrose process. We elucidate when such a process is possible and give full classification of corresponding relativistic objects for rotating space-times. We also discuss the case of a pure electric super-Penrose process that is valid even in the flat space-time. The key role in consideration is played by the Wald inequalities.

Electron-proton interaction in radio sources

A method of treating electron-proton interaction is presented. The energies involved in the interaction are estimated. Only elastic collisions are considered. The cross sections of the processes are not taken into account. Calculations are carried out in the centre of mass frame. Relevant quantities are transformed into the laboratory frame. Results indicate that the energy per collision gained by an electron ranges from 0.5 MeV to 0.6 MeV, under suitable conditions.

Production cross-section of heavy flavored hadrons in pp collision at s = 7 TeV

The transverse momentum distribution of the differential production cross-sections of heavy flavored charm hadrons [Formula: see text], [Formula: see text] in pp collisions at 7 TeV are simulated. Predictions of DPMJETIII.17-1, HIJING1.383 and Sibyll2.3c are compared to the differential cross-section measurements of the LHCb experimental data presented in the region of [Formula: see text] and [Formula: see text], where the pp center of mass frame is used to measure the transverse momentum and rapidity. The models reproduce only some regions of [Formula: see text] and/or bins of [Formula: see text] but none of them predict completely all the [Formula: see text] bins over the entire [Formula: see text] range.